feat: forum rich-text editor, emoji picker, mentions, discover nav, feed, uploads, profile

Forum:
- TipTap WYSIWYG editor with full toolbar
- @emoji-mart/react emoji picker (consistent with tweets)
- @mention autocomplete with user search API
- Fix PHP 8.4 parse errors in Blade templates
- Fix thread data display (paginator items)
- Align forum page widths to max-w-5xl

Discover:
- Extract shared _nav.blade.php partial
- Add missing nav links to for-you page
- Add Following link for authenticated users

Feed/Posts:
- Post model, controllers, policies, migrations
- Feed page components (PostComposer, FeedCard, etc)
- Post reactions, comments, saves, reports, sharing
- Scheduled publishing support
- Link preview controller

Profile:
- Profile page components (ProfileHero, ProfileTabs)
- Profile API controller

Uploads:
- Upload wizard enhancements
- Scheduled publish picker
- Studio status bar and readiness checklist

resources/js/components/Feed/LinkPreviewCard.jsx

@@ -0,0 +1,96 @@
+import React from 'react'
+
+/**
+ * LinkPreviewCard
+ * Renders an OG/OpenGraph link preview card.
+ *
+ * Props:
+ *   preview     { url, title, description, image, site_name }
+ *   onDismiss   function|null  — if provided, shows a dismiss ✕ button
+ *   loading     boolean        — shows skeleton while fetching
+ */
+export default function LinkPreviewCard({ preview, onDismiss, loading = false }) {
+  if (loading) {
+    return (
+      <div className="rounded-xl border border-white/[0.08] bg-white/[0.03] overflow-hidden flex gap-3 p-3 animate-pulse">
+        <div className="w-20 h-20 rounded-lg bg-white/10 shrink-0" />
+        <div className="flex-1 min-w-0 flex flex-col gap-2 justify-center">
+          <div className="h-3 bg-white/10 rounded w-2/3" />
+          <div className="h-2.5 bg-white/10 rounded w-full" />
+          <div className="h-2.5 bg-white/10 rounded w-4/5" />
+          <div className="h-2 bg-white/[0.06] rounded w-1/3 mt-1" />
+        </div>
+      </div>
+    )
+  }
+
+  if (!preview?.url) return null
+
+  const domain = (() => {
+    try { return new URL(preview.url).hostname.replace(/^www\./, '') }
+    catch { return preview.site_name ?? '' }
+  })()
+
+  return (
+    <div className="relative rounded-xl border border-white/[0.08] bg-white/[0.03] overflow-hidden hover:border-white/[0.14] transition-colors group">
+      <a
+        href={preview.url}
+        target="_blank"
+        rel="noopener noreferrer nofollow"
+        className="flex gap-0 items-stretch"
+        onClick={(e) => e.stopPropagation()}
+      >
+        {/* Image */}
+        {preview.image ? (
+          <div className="w-24 shrink-0 bg-white/5">
+            <img
+              src={preview.image}
+              alt=""
+              className="w-full h-full object-cover"
+              loading="lazy"
+              onError={(e) => { e.currentTarget.parentElement.style.display = 'none' }}
+            />
+          </div>
+        ) : (
+          <div className="w-24 shrink-0 bg-white/[0.04] flex items-center justify-center text-slate-600">
+            <i className="fa-solid fa-link text-xl" />
+          </div>
+        )}
+
+        {/* Text */}
+        <div className="flex-1 min-w-0 px-3 py-2.5 flex flex-col justify-center gap-0.5">
+          {preview.site_name && (
+            <p className="text-[10px] uppercase tracking-wide text-sky-500/80 font-medium truncate">
+              {preview.site_name}
+            </p>
+          )}
+          {preview.title && (
+            <p className="text-sm font-semibold text-white/90 line-clamp-2 leading-snug">
+              {preview.title}
+            </p>
+          )}
+          {preview.description && (
+            <p className="text-xs text-slate-500 line-clamp-2 leading-relaxed mt-0.5">
+              {preview.description}
+            </p>
+          )}
+          <p className="text-[10px] text-slate-600 mt-1 truncate">
+            {domain}
+          </p>
+        </div>
+      </a>
+
+      {/* Dismiss button */}
+      {onDismiss && (
+        <button
+          type="button"
+          onClick={(e) => { e.stopPropagation(); onDismiss() }}
+          className="absolute top-1.5 right-1.5 w-5 h-5 rounded-full bg-black/60 hover:bg-black/80 text-slate-400 hover:text-white flex items-center justify-center transition-colors text-[10px]"
+          aria-label="Remove link preview"
+        >
+          <i className="fa-solid fa-xmark" />
+        </button>
+      )}
+    </div>
+  )
+}